1. Field of the Invention
The invention relates to halogenated or pseudohalogenated monomeric phenazinium compounds, to a method of preparing same, to an acidic bath containing said compounds for electrolytically depositing a copper deposit as well as to a method of electrolytically depositing a copper deposit using said acidic bath. The halogenated or pseudohalogenated monomeric phenazinium compounds may be used as additives in copper plating baths to more specifically form mirror bright level deposits of copper in order to produce decorative surfaces. The compounds may moreover be used as additives in copper plating baths to selectively and completely fill with copper blind microvias in printed, circuit boards and trenches and vias on semiconductor, wafers. The compounds may also be utilized as additives in copper plating baths for depositing copper onto semiconductor substrate surfaces provided with recesses during the manufacturing process of integrated circuits, with the entire semiconductor substrate surface being uniformly coated with copper.
2. Brief Description of the Related Art
For depositing bright copper surfaces, organic additives are usually added in small quantities to most of the acidic copper electrolytes in order to obtain bright copper layers instead of a crystalline matte deposit. In this approach, an additive compound or a combination of several additive compounds such as polyethylene glycols, thioureas and the derivatives thereof, thio hydantoin, thio carbamic acid esters as well as thio phosphoric acid esters is often added. Nowadays however, the additives mentioned are no longer significant, due to the fact that the quality of the thus obtained copper layers meets by no means today's requirements. The thus obtained coatings are either too brittle or exhibit poor brightness and insufficient leveling.
The utilization of certain phenazinium compounds such as phenazine dyestuffs e.g., safranines and of the derivatives thereof, that are also used as paper and leather dyes and as dyes for keratin-containing fibers, has long been known for producing bright copper layers. In accordance with DE-PS 947 656, these dyes, e.g., dimethyl safranine azo dimethyl aniline, diethyl safranine azo dimethyl aniline, Janus grey and safranine azo naphthol are being used as the only additives. It is moreover known to use said compounds in combination with other additives as well.
Further, DE-AS 1 521 062 suggests bath compositions containing an organic sulfide that contains at least one sulfonic acid group as well as, mixed thereto or chemically bonded, a polyether that contains at least three, preferably six, oxygen atoms and is free of aliphatic hydrocarbon chains having more than six C-atoms. These baths permit deposition of smooth, bright and ductile copper layers. Preferred polyethers mentioned are 1,3-dioxolane polymerisates having a molecular weight of at least 296, preferably of about 5000. Phenazine dyestuffs may also be utilized in combination with the bath additives mentioned, for example diethyl phenosafranine azo dimethyl aniline, dimethyl phenosafranine azo dimethyl aniline, diethyl phenosafranine azo phenol and dimethyl azo-(2-hydroxy-4-ethylamino-5-methyl)-benzene. The phenazine dyestuffs permit high leveling and a wide range of bright deposits.
With the copper electrolytes described in DE-AS 1 521 062 however it is not possible to utilize a higher cathodic current density. Moreover, the deposited copper surfaces can only be nickel-plated after having been subjected to a preliminary intermediate treatment.
It is further known to use hydroxylated and halogenated phenazine dyestuffs of the safranine type as-levelers and brighteners, such as DE-OS 2 028 803. This document relates to polymeric phenazinium compounds, the phenazinium skeletale structure being substituted with hydrogen, lower alkyl or substituted or unsubstituted aryl.
1973:43420 CAPLUS relating to A. Ya. Il'chenko and V. N. Rudenko in: Khimiya Geterotsiklicheskikh Soedinenii (1972), (10), 1425-1429 schematically discloses the synthesis of 3-chloro-5-methyl-7-(phenylamino)-phenazinium perchlorate.
The use and production of monomeric halogenated phenazine dyestuffs for acidic copper baths is i.a. described In the Patent Abstracts of Japan corresponding to JP 60-056086 A. The dyestuffs are prepared in a two-stage synthesis consisting of a diazotization reaction and of a halogenation reaction. For diazotization, the corresponding safranine dyestuff is first dissolved in the heat and filtered. At a temperature of 0 to 5° C., it is then diazotized with sodium nitrite and later hydrochloric acid being added before it is finally heated. Once it has cooled down, the reaction solution is reacted at room temperature over a period of 10 hours in the presence of copper(II) chloride solution, copper powder and hydrochloric acid to form the chlorinated phenazine dyestuff. It describes, by way of example, the preparation of 7-diethylamino-3-hydroxy-5-phenyl-phenazinium sulfate, of a mixture of 3-chloro-7-diethylamino-5-phenyl-phenazinium chloride and 7-diethylamino-3-hydroxy-5-phenyl-phenazinium chloride and of 3,7-dichloro-2,8-dimethyl-5-phenyl-phenazinium chloride.
The disadvantage of the method described is that for each synthesis step, inclusive of the dissolution of the dyestuff, a separate reaction vessel is needed. As a result of the long reaction times and of the moderate stability of the diazonium compounds, which easily decompose in an acidic medium, uncontrolled reactions may take place, resulting in variable quality of the products desired. Moreover, such type of time-consuming reactions is very expensive from an economical point of view.